1. Field of the Invention
This invention relates to a sheet transfer system which conveys sheets attracting the back side thereof under vacuum without contacting the front side of the sheets for use, for instance, in a sheet sorter which is provided with a plurality of bins each of which receives a plurality of sheets discharged from an image recording apparatus such as a printer, a copier or the like and forms thereon a stack of sheets.
2. Description of the Related Art
Generally sheets are conveyed held between a pair of conveyor rollers. However in the case of sheets carrying thereon wet ink like printed sheets just discharged from a printer such as a stencil printer, such conveyor rollers cannot be used since the rollers are contaminated with ink and the images on the sheets are deteriorated through contact of the rollers with the printed sides of the sheets. Accordingly sheets wet with ink are conveyed by a system which conveys sheets attracting the back side thereof under vacuum without contacting the front side of the sheets.
In order to make compact an apparatus such as a sheet sorter, it is necessary to bend the conveyance passage of the sheets, for instance, at an acute angle.
In the case of a transfer system in which the sheets are conveyed with the back side thereof attracted against a conveyor belt under vacuum, it is difficult to attract the sheets so that the sheets are sufficiently bent along the bent conveyance passage unless a substantially large suction apparatus is used since the sheets are spaced from each other and the vacuum system is not closed. Especially when the sheets are large in thickness or the conveying speed is high, the leading end portion of the sheet will project outside the conveyance passage away from the conveyor belt when passing the bent portion of the conveyance passage, which can result in jam of the transfer system.